In devices such as scanning electron beam devices and ion beam devices that scan and measure by irradiating samples with a charged particle beam the problem of irradiation from the primary charged particles causing static charges has long been a serious problem.
When a sample containing insulation material such as a sample containing a wiring pattern formed on an interlayer dielectric film or semiconductor substrate coated with resist is irradiated by an electron beam, that sample becomes statically charged and voltage potential of that static charge causing problems such as bending the primary charged particle beam track, focusing errors and astigmatisms. When these types of phenomena occur, making accurate inspections and measurements is impossible because secondary electron or reflected electron distribution data cannot be obtained that accurately reflects the material distribution and surface contours of the sample. This problem becomes worse as the size of the inspection or measurement target becomes smaller, such as the size of the semiconductor wiring (layer) width or the liquid crystal transistor.
The technology in JP-A-Hei10(1998)-125271 discloses an adjusting unit that adjusts the value of the retarding voltage applied to the sample to offset the static charge, and suppress fluctuations in the quality the scanning electron image obtained in this way. The technology in JP-A-2001-236915 discloses a technology for calculating a static charge map of the material surface, and optimizing the incident energy of the irradiating electron beam according to the static charge voltage from the position where the primary charged particle beam is irradiated, and adjusting the focus of the primary charged particle beam. The technology in WO03007330 discloses a method for measuring localized voltages on the surface of the sample by utilizing an energy filter to acquire the S curve of the secondary electrons. The value measured as the localized static charge voltage is fed back to a deflected signal setting of a scanning deflector to change the image magnification by adjusting the intensity of the deflected signal, and eliminate effects from the localized static charge. In the invention disclosed in WO03007330, there are two types of static charges. One static charge type is a broad region charge and the other type is a localized charge. The broad region charge greatly affects the focus of the charged particle beam and the localized charge greatly affects the magnification of the charged particle beam. These charges must be isolated for measurement.
The invention in JP-A-2003-202217 on the other hand, discloses technology for irradiating a planar beam onto a sample applied with a voltage potential nearly equal the accelerating energy of the charged electron beam, and focusing the charged particle beam planar-reflected from the sample in this state to examine the sample.